Fox confirmed Tuesday that Carey had signed on to judge the singing competition, which begins airing new episodes in January. She subsequently Tweeted: "It's gonna be so much fun working on @AmericanIdol. As a singer-songwriter, I'm excited to help find and nurture new talent. LYM! —MC"

With former judges Steven Tyler and Jennifer Lopez announcing their departures last week, there's no word yet who will fill the third judge's seat.